The social media site demonstrated solid growth in its most-watched measurement — monthly active users (MAUs) — in its second-quarter earnings report on Tuesday. An unexpected profit, a positive outlook and growing revenue per 1,000 timeline views (a Twitter metric for how well it is making money from its platform), all pointed to brighter days ahead.

Investors responded in kind, as shares in the social media company, which had been battered in 2014, shot up as much as 35% in after-hours trading, settling closer to 25% on Wednesday morning before the market open.

The sudden turn of positivity should help Twitter bide its time on a mounting challenge: making money from its content appearing on websites, television and mobile apps.

During Tuesday's earnings call, CEO Dick Costolo made the case for including passive users in its advertisers' calculations:

Beyond our 271 million monthly active users, there are hundreds of millions of additional unique visitors who come to Twitter every month but don’t log-in," Costolo said. "When you consider the combination of monthly active users and unique visitors, the size of our audience on our owned and operated properties is two to three times that of just our monthly active user base, which we believe ranks us among the top-10 largest digitally connected audiences in the world.

Costolo added that the company is running experiments to "improve the overall experience for logged out unique visitors."

It's not clear whether Costolo's emphasis on casual users was merely designed to change the subject from monthly active users, the industry's standard metric. Monthly active user growth has been a struggle for Twitter, with current growth levels far below what the company had predicted.

Once routinely compared to Facebook, Twitter might now be considered the leader of the second tier of niche social media sites, at least as measured by MAUs.

What's frustrating for Twitter is that its outsized influence — only 15% of the U.S. public is on the platform, but it's all but impossible not use it as a journalist — means that a lot of non-users consume Twitter content. Rich Greenfield of BTIG Research noted in a blog post that "off-Twitter MAUs," or people who end up consuming Twitter content through other platforms not tied to the social media company, are growing at a rate 10 times that of traditional MAUs.

The key for Twitter will be whether it can convince marketers that this audience is reason enough for Twitter to charge more for its advertising.

"With the off-Twitter MAUs we are far from certain how/when monetization will occur, if ever. The potential of off-Twitter monetization is a critical issue for management to address going forward," Greenfield wrote on his BTIG Research blog.

Reports have indicated that Twitter is preparing a series of new metrics that will attempt to capitalize on this audience. There had been some anticipation that this would coincide with second-quarter earnings, but as Re/code's Peter Kafka predicted, Twitter did not release anything about this.

New metrics could help, but they would only be half the battle.

Twitter has figured out how to monetize its existing user base, but new metrics that demonstrate reach will not necessarily translate into more ad dollars, said Sean Muzzy, CEO of Neo@Ogilvy North America, the agency's performance marketing arm.

"It has never been the case that we're just going to pay more for somebody that has more eyeballs. There still has to be that value exchange with the advertiser, the publisher of the content and the consumer that's going to be part of that dialogue that the brand's trying to create," he said. "Reach alone isn't the answer."

He added that Twitter will need to figure out the best way to generate money from its reach, whether that is through content deals with publishers or the monetization of actual tweets, much like Facebook has done with brands and Google with its content network.

One possibility is that Twitter will use these metrics explore new revenue streams. Acquisitions such as CardSpring for ecommerce and SnappyTV for television promotion have hinted at income that goes beyond advertising. Currently 89% of Twitter's revenues come from advertising. The rest is generated by Twitter's data business.

A Twitter spokesperson declined to comment on any future plans to introduce new audience metrics.

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